The long term objective of our research is a better understanding of how sounds are processed in complex acoustical environments, and a unification of our understanding of different facets of auditory perception. In the proposed research we will continue to examine the acuity with which one can lateralize simple sounds in the presence of various different types of tonal and broadband maskers, and we will extend these experiments to characterize the perception of stimuli with time-varying binaural cues. We will also include in our experimental program studies designed to unify our understanding of mechanisms mediating binaural lateralization and complex pitch perception. The proposed research consists of a combination of psychoacoustical experiments and theoretical modeling of various attributes related to the lateralization of binaural stimuli, and to the formation of unified perceptual images from complex sounds. The experimental program is directed toward obtaining a better understanding of the acuity with which one perceives the subjective position of binaural sounds, and the robustness characterizing their perceived pitch. These experimental results will be used to extend our theory of binaural perception to describe stimuli with time-varying interaural differences, and to describe stimuli giving rise to the formation of central dichotic pitch percepts. This theory, which is based on a hypothetical central processor that performs specific operations on the auditory-nerve response to a given acoustical stimulus, has successfully described and predicted subjective and objective perceptual attributes of less complex binaural sounds. The results of the proposed work should provide major improvements in our understanding of the spatial perception of complex acoustical stimuli, the perception of moving sound sources, and relationships between complex pitch and auditory lateralization. They will also be of value in the design of sensory aids for persons with visual or auditory impairments.